Abstract
Surface albedo is an important driver of surface processes that promote glacier melting and is a key variable influencing glacier surface melt. Despite much focus in the literature on variation in albedo and its influence on snow surfaces, little attention has been paid to dust and its impact on bare-ice albedo with respect to glacier melting surfaces. In this paper, spatial changes in glacier albedo were investigated using three Landsat images taken during the ablation season in 2006; temporal variations in albedo were measured by an automatic weather station in the ablation zone between 26 June and 1 August 2007, at Urumqi Glacier No. 1 in Tien Shan. Ice and snow samples, and reflection spectra at 325–1050 nm were collected in August, 2007 at Urumqi Glacier No. 1. The data suggested that spatial changes in glacier albedo are not prominent after snowfall; however, once ice becomes exposed, glacier albedo varies remarkably and generally increases with elevation, especially around the equilibrium line. Temporal variations are characterized by a large range and high frequency, and most are induced by snowfall, changes in cloud conditions, and surface dust; snowfall and cloud increase glacier albedo. Furthermore, the response of snow albedo is more sensitive to cloud compared with the response of ice albedo. Over a bare ice surface, the albedo generally decreases as the concentration of surface dust increases. Organic matter is a primary factor in reducing the albedo over ice.
Highlights
An important source of freshwater, it is well known that mountain glaciers are seriously threatened by global climate change
Albedo is higher in the morning and afternoon than at noon, but asymmetry around solar noon is more pronounced; this phenomenon is likely to result from the change in solar zenith angle, while reduced afternoon values result from snow metamorphism and surface melt
Minimal indications of diurnal albedo cycles were found between 22 and 27 July over ice surfaces, which implies that the effect of solar zenith angle
Summary
An important source of freshwater, it is well known that mountain glaciers are seriously threatened by global climate change. A widespread decrease in the extent of glaciers and a continuous loss of glacier mass have been observed over the past 50 years (Zemp et al, 2019). On the Peyto Glacier, Munro (1991) reported that an increase of 0.05 in glacier albedo caused a change in mass balance of 0.66 m w.e., while mass balance changed −0.83 m w.e. with a decrease in glacier albedo of 0.05 This high sensitivity is linked to a positive feedback mechanism between glacier melt and surface albedo, involving enhanced melting and increased exposure of bare ice; aggregated impurities and meltwater on the glacier’s surface; and reduced surface albedo and increased solar radiation absorption, accelerating melt (Klok and Oerlemans, 2004; Moustafa et al, 2015). Significant motivation exists to investigate the temporal and spatial variation in glacier albedo to reveal the response mechanism of glaciers to climate change
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